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View Full Version : Analogy and Comparability of wiggly rope to quantum leap?



sirius0
2012-Jul-31, 01:24 AM
As I understand a quantum leap for say an electron from one 'orbit' to another it doesn't actually have any presence while traversing unallowed space in between. It just leaps from one point to the other. (from one energy level to another) Perhaps I am wrong? don't think so... Is it fair or reasonable, in order to promote some sort of intuitive understanding to relate this to the 'flat' rope that occurs when two waves 180 degrees out of phase meet on a rope?

Shaula
2012-Jul-31, 05:53 AM
Electrons don't orbit though. So any analogy based on them doing so is kind of misleading.

sirius0
2012-Jul-31, 10:12 AM
Electrons don't orbit though. So any analogy based on them doing so is kind of misleading.

My intent is not to make an analogy of orbits to the quantised momenta of electrons energy levels. I used orbit to frame my question about a possible analogy between wave cancellation in a rope to the transit (another framing word) of an electron from one energy level to another. As a sidetrack from the subject i don't consider electrons to orbit in the Copernicus/Newton/Kepler sense either, I see them more as some kind of standing wave.

So about waves in ropes and quantum leaps (oh and I do see that i have leaps, a particle thing, with cancellation, a wave thing. wave particle duality does not worry me for this analogy I am hatching)

Shaula
2012-Jul-31, 02:32 PM
Not a fan on analogies when pretty much every term in the analogy is a poor fit to the model they are trying to shed light on.

sirius0
2012-Jul-31, 03:41 PM
Not a fan on analogies when pretty much every term in the analogy is a poor fit to the model they are trying to shed light on.

I think analogies are by definition poor fits. So how did you establish your current understanding? Where did you start from? If there is a better way i would like to know.

Analogies are used all the time. You pointed out that electrons don't actually orbit, not the core of my thread, but this term has been used many times over as an analogy. Perhaps it does not sound proffesional enough or knowledgable enough, however, i thought in this forum it would, out of respect for the level of knowledge of my peers, be understood not to mean the classic sense. i don't think using the word orbit for a particle/wave/wavepacket thing is any more erroneous than advanced physicists using terms like Spin (very misleading!), Charm, Up, Down and Coloured. All these terms draw the analogy and some are very weak associations.

Shaula
2012-Jul-31, 04:41 PM
So how did you establish your current understanding? Where did you start from?
School -> Library -> University. I guess you are trying to get me to admit that I used analogies myself. Well, true, I did. But I did not dwell on them and I did not spend too much time trying to use them to reason my way to things. Because analogies are intrinsically weak ways to understand things.

And colour, strangeness, charm - these are not analogies. They are just names.

I guess my point is that once you get to the level of explaining how electrons make transitions from one state to another you are so far from particles hopping around I see no point in using analogies based on them. Your statement that an electron cannot enter a forbidden reason is dripping with classical assumptions of localisation. Electrons do no jump around, the shape of the probability cloud changes. When you get down to trying to explain how this happens I see no value in an analogy that encourages classical thinking.

sirius0
2012-Aug-01, 12:11 AM
School -> Library -> University. I guess you are trying to get me to admit that I used analogies myself. Well, true, I did. But I did not dwell on them and I did not spend too much time trying to use them to reason my way to things. Because analogies are intrinsically weak ways to understand things.

And colour, strangeness, charm - these are not analogies. They are just names.

I guess my point is that once you get to the level of explaining how electrons make transitions from one state to another you are so far from particles hopping around I see no point in using analogies based on them. Your statement that an electron cannot enter a forbidden reason is dripping with classical assumptions of localisation. Electrons do no jump around, the shape of the probability cloud changes. When you get down to trying to explain how this happens I see no value in an analogy that encourages classical thinking.

OK thank you. I have no arguament with what you are saying really. What you say is true about how I may understand things, however, I get some pretty big questions from year 5 & 6 students once the possible Higgs Boson was found. It is their questions that motivated my thread. Whenever I use an analogy I point out the limits etc but they need some initial access.

Shaula
2012-Aug-01, 08:30 AM
Ah, OK. That is a really tricky one then, I was assuming it was for personal consumption!

Best analogy I ever saw was the drumskin. It is similar to standing waves one - orbitals are akin to different modes on a drumskin, and changes between them are just changes in the dominant mode. But good luck finding an analogy - when using one to a group of kids who ask questions all analogies are equally in trouble.

John Jaksich
2012-Aug-01, 11:33 AM
Ah, OK. That is a really tricky one then, I was assuming it was for personal consumption!

Best analogy I ever saw was the drumskin. It is similar to standing waves one - orbitals are akin to different modes on a drumskin, and changes between them are just changes in the dominant mode. But good luck finding an analogy - when using one to a group of kids who ask questions all analogies are equally in trouble.
on

The thing about telling children about QM --I am of the opinion that (such concepts) are best suffused through fun---if you happen to be an expert (?) on such a subject--and you're having a "normal" lifestyle ----> where you don't find yourself "robbing Paul to Pay Peter" kind of analogy.

Children pick things up rather readily if there is a "good" learning environment for them ----> putting things in adult terms does not and is not conducive to learning science for a child....that is the bottom line. You will find that you will alienate a child if attempt teach such an abstract concept as if he or she were your colleague. I am sure that will sound like a no-brainer to most of us.

I can remember (very long ago---as a child) being in a situation of where fifty of us had a hold of a parachute and putting a basketball onto it and having opposite and adjacent sides attempt to move the heavier ball along------> currently, it reminds me field lines, gravity, and possibly a little bit of QM thrown in for good measure. I can remember having fun! -----> but years later ----> it formed an indelible impression upon me when attempting to understand Relativity----> I am certain most of us have seen simulations of gravity wells and orbits of planets.


That recreational activity was very educational and not presented as an attempt to suffuse field lines not gravity at the time.

I hope it makes some sense---in that Students find it easier to learn when they don't know that they are learning something of great importance----> but are also enjoying themselves.

sirius0
2012-Aug-09, 10:31 PM
Shaula & John Jaksich
This has been excellent advice. In the end I took along a bottle of dyed water and oil, this slows the waves drastically and is very impressive, yellow oil and bright blue water ( I picked this up of the Naked Scientists podcast). I also got them to play with a rope tied to a door nob. Next week it is string and cans telephone and a slinky spring connected between props. After that it will be a sealed tray with water, a wave tank. Basically I just said that "a lot of the questions about particles and quantum were partly based on how waves work, now lets explore waves". No further analogy than that (John their minds have been thoroughly seeded). We have seen waves sum amplitude and cancel, we have seen transverse and longitudinal waves. I guess Doppler will come soon all just experiential, some explanation. Good good good! Any other suggestions appreciated.

Shaula, the drum idea was good. When I turned the oil/water bottle on its end I got the transverse modes which due to the surface tensions were basically the same as a slow moving drum.

I am a volunteer via a CSIRO program called "Scientists in Schools" I work as an engineer in automation but a number of times a term I attend and give them some time. They have seen my work place and it is always good to show how science is every day relevant. Their eyes shine and I think there may be some future scientists in the class. :)

Shaula
2012-Aug-10, 06:14 AM
I am a volunteer via a CSIRO program called "Scientists in Schools" I work as an engineer in automation but a number of times a term I attend and give them some time. They have seen my work place and it is always good to show how science is every day relevant. Their eyes shine and I think there may be some future scientists in the class.
Must be very rewarding - I used to do something similar but we never got as far as quantum theory! The teachers generally just wanted us to blow something up or shoot something into the air. It was a lot of fun but I couldn't help but feel that telling people that physics and chemistry are about how to blow stuff up might lead them to disappointment later on. :D